Magnesia carbon bricks have become the preferred material for key parts of ladle furnaces and converters due to their resistance to high temperatures, thermal shock and slag erosion. However, the problem of carbon damage during the preheating process needs to be solved by covering with composite antioxidants and alkaline liquids to significantly improve service life and production efficiency.
Application background of magnesia carbon bricks
In modern steel production, magnesia-chromium refractories are gradually being replaced by magnesia-carbon bricks due to environmental impacts. Magnesia-carbon bricks, as an alternative material, now perform key refractory functions in ladle furnaces and ladles. In refining ladle furnaces and ladles, MgO-C bricks are primarily used in key areas such as the headroom and slag line. These areas place stringent requirements on refractory materials, including resistance to high temperatures, thermal shock, and slag erosion.
However, magnesia carbon bricks face a significant problem in production applications: the carbon in the bricks is severely degraded during the preheating process. New magnesia carbon bricks in a new ladle can have a loose, decarburized layer as thick as 30 to 60 mm. This layer is washed away during the injection of molten steel, allowing magnesia sand particles to enter the slag. To prevent this, composite antioxidants and alkali-containing low-melting glass phase liquids are added to the surface of the magnesia carbon bricks to extend their service life.
Application of magnesia carbon bricks on converter lining
Furnace mouth and furnace cap area
In the converter, magnesia carbon bricks are used in the furnace mouth and furnace cap area because of their resistance to slag erosion and spalling, which can well adapt to frequent thermal shocks. This area requires refractory materials that can withstand the erosion of high-temperature slag and high-temperature exhaust gas, while also being easy to clean hanging steel.
Application on the charging side and slag line area
The requirements for MgO-C bricks in the charging side and slag line area are more stringent. They not only require high resistance to slag erosion, but also good high-temperature strength and spalling resistance. Especially under high temperature conditions, MgO-C bricks need to be able to maintain high strength to prevent damage, thereby ensuring the normal operation of the converter.
Application of magnesia carbon bricks in electric furnace
Electric furnace masonry and quality influencing factors
In electric furnaces, the quality of magnesia carbon bricks is directly related to the furnace’s service life. The quality of magnesia carbon bricks is affected by a variety of factors, including the purity of the magnesia, the types of impurities, and the bonding state and size of the periclase grains. Furthermore, the purity, degree of crystallization, and flake size of the flake graphite used as the carbon source also significantly impact its quality.
Erosion behavior at the slag line
At the slag line, magnesia carbon bricks will experience significant corrosion, which is manifested as the formation of a decarburized loose layer and a reaction dense layer. The slag line has typical corrosion behavior, which requires the addition of alkali-containing low-melting glass phase liquid to alleviate this corrosion, thereby increasing the service life of magnesia carbon bricks in this area.
Taphole design and application cases
There are two approaches to tapping an electric furnace: tilting the tapping chute and tapping from the furnace bottom. By rationally designing and applying magnesia-carbon bricks, and employing different design approaches, the tapping life can be extended, significantly increasing furnace life and production efficiency. For example, one steel mill’s furnace life increased from approximately 60 furnaces to more than double after using magnesia-carbon bricks.
Application of aluminum-magnesium-carbon bricks in ladle
Application in clearance and slag line areas
In refining ladle furnaces and ladles, magnesia carbon bricks are used to replace traditional materials in areas with strict clearance and slag lines. These areas require refractory materials that can withstand high temperatures, thermal shock, and mechanical corrosion such as slag erosion.
Problems in the preheating process of magnesia carbon bricks
The carbon content of MgO-C bricks in new ladles is severely damaged during the preheating process, which shortens the service life of the bricks. By adding a composite antioxidant and an alkaline liquid to the surface, the carbon content in the MgO-C bricks can be effectively protected from being burned during the preheating process.
